I'm getting around 1000 to 1200 sf/hour using OP and around 750 per hour using HWE. So, in my maintenance accounts, I am OP cleaning on most occasions as a maintenance system and HWE'ing when needed as a restorative process.
I can usually keep the carpets "looking" clean for months and months ... even years in some cases ... using OP (padcapping), but as soon as I flush with HWE I see the rinse water black with filth.
Nothing beats a good HWE flush every now and then.
I agree with Martin; HWE is the only way to go; I don't do anything but HWE; Restaurants are to greasy and way to high traffic for anything but HWE; I would definently use agressive degreasing in Restaurants followed by pretreating and the hottest water extraction you can do; you will keep custy very happy.